Thread: Valve guide repair

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Everybody has given great solutions as far as this question goes. I noticed in the initial post, the concern seemed to be more of a BTU question. Butane, Propane, Natural gas, etc are a concern of vaporization on entering the cylinder. It's a dry fuel therefore the worry would more in the line of guide lubrication. As far heat goes, I like to think about my seats for duration of the cycles this thing goes through. It's a bummer that guide replacement is a tad high in Germany. Better safe than sorry I suppose should be the response to that.

Sure better safe than sorry
The heads are GM 492 casts (thick castings). Valves are 1.94 and 1.50, 3 of the valves of this set of heads have oversized stems already, and they aren't worn yet. The others are (it wasn't me ). This won't be a racer, just around 300hp. It is only going to be a rebuild, just bored to a 355 with flat tops and a street cam, engine is going in a 1970s Impala.
The reason I don't want to knurl is exactly the hourglass shape of the guides. I will have to measure them exactly (haven't done so yet, but some seem to be past knurling, especially as the top of the guides are pretty worn.)
I have two problems:
1: I live in Germany, where special parts are difficult to get (oversized valves etc.)
2: I don't build many engines, maybe one a year, at the moment I'm doing two, but that isn't very often.
Especially reason two means I want to buy as little tools as possible for one specific job. If I buy a knurling set now for 50 bucks because the heads will be OK knurled, and in a year I get some heads where knurling won't do anymore, I'll have to get the drill-pressfit solution anyway. So I'd rather go there now. Or the oversized valve-solution, I don't know what could be a problem there? The valves are certainly a bit heavier, but if I use oversized valves with undercut stems surely the weight difference will be minimal
That seems to be by far the easiest and cheapest solution to me...

PS: The way I usually go is only to buy heads which I know are OK. This time I bought a whole engine (for really small money) and found out it had good heads (except for the guides), a new block, forged pistons and an Edelbrock cam set in it (I had actually only bought it for the connecting rods, the price for them would have been OK even if the rest was junk ). Lucky on that one, but now of course I want to make the best of that bargain

I'll have a look at PEP's big stem valves in a minute...

OK, then I'll check the guides exactly at the weekend and come back here again later. The engine ran OK, I didn't check the rocker geometry before tearing it apart, I never used this engine. I only know that it ran OK, just used some oil. But as it didn't have positive valve stem seals that would be sure to be the case.
You'll hear from me soon,
Max

Knurling, whether finished by reaming or swedging, involves displacing the parent guide material to reduce clearance. It is a short-lived repair.

tom